/* Copyright 2025 The OpenXLA Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
==============================================================================*/

#ifndef XLA_SERVICE_DEBUG_UNSTABLE_REDUCTION_DETECTOR_H_
#define XLA_SERVICE_DEBUG_UNSTABLE_REDUCTION_DETECTOR_H_

#include "absl/container/flat_hash_set.h"
#include "absl/status/statusor.h"
#include "absl/strings/string_view.h"
#include "xla/hlo/ir/hlo_module.h"
#include "xla/hlo/pass/hlo_pass_interface.h"

namespace xla {

// A pass that checks for unstable reductions in a module. If the module has
// unstable reductions, the pass will log them or crash depending on the value
// of the xla_detect_unstable_reductions debug option.
//
// We define an unstable reduction instruction as a reduce instruction that
// accumulates something other than a maximum or a minimum, and whose
// accumulation type is a floating point type smaller than f32.
class UnstableReductionDetector : public HloModulePass {
 public:
  absl::string_view name() const override {
    return "unstable-reduction-detector";
  }

 protected:
  absl::StatusOr<bool> RunImpl(
      HloModule* module,
      const absl::flat_hash_set<absl::string_view>& execution_threads) override;
};

}  // namespace xla

#endif  // XLA_SERVICE_DEBUG_UNSTABLE_REDUCTION_DETECTOR_H_
